In the customary emulsion polymerization process for producing vinyl resins, water-soluble polymerization initiators are generally employed so that latex or paste of acceptable properties can be provided. On the contrary, oil-soluble polymerization initiators are employed in the microsuspension polymerization process for producing vinyl polymers or copolymers. No matter which of said processes is adopted, a large amount of emulsifier or emulsifiers must be included in the polymerization recipe. As examples of such emulsifiers may be mentioned the anionic surfactants, such as a high fatty acid soap, a sulfate of a long chain alcohol, a metallic salt of an alkyl benzene sulfonate, and the like, nonionic surfactants, such as a glycerin ester of fatty acids, a sorbitan ester, a polyol ester of fatty acids, a polyoxyethylene compound and the like.
It has been known that the resins obtained from said emulsifier-incorporated polymerization processes will have emulsifier residue contained within the polymer particles which has adverse effects on the properties of the resins. Accordingly, when the resins are formulated into plastisol or organosol for further processing, the viscosity changes during storage are somewhat unacceptable, the heat stability thereof is undesirable, and the clarity of the products made therefrom is to be improved. In view of the adverse effects emulsifiers have on the properties of the resins, it is obvious that great advantages can be obtained if emulsifiers are deleted from the polymerization recipe. However, if the emulsifiers are not included in the recipe, the stability of colloidal particles during polymerization remains much to be improved. It is therefore an aspect of the invention to provide a polymerization process which does not incorporate emulsifiers in its polymerization recipe, yet acceptable stability of colloidal particles during polymerization is provided as well.